Macroporous Directed and Interconnected Carbon Architectures Endow Amorphous Silicon Nanodots as Low-Strain and Fast-Charging Anode for Lithium-Ion Batteries

Highlights MPCF@VG@SiNDs/C, constructed by uniformly dispersing amorphous Si nanodots in carbon nanospheres that are welded on the wall of the macroporous carbon frameworks by vertical graphene, is synthesized and has achieved a few kilogram production per batch. Finite element imitation reveals that amorphous Si nanodots with high dispersity in carbon nanosphere can achieve ultra-low stress and strain values during lithiation. Unique low-strain property and fast-charging capability are achieved under industrial electrode conditions. Supplementary Information The online version contains supplementary material available at 10.1007/s40820-023-01308-x.


S2 Supplementary Figures and Tables
The electronic platform scale has been peeled, i.e., the mass of the glass container has been deducted.That is, the total amount of MPCF@VG@SiNDs/C obtained after one preparations is 4.9 kg.Table S2 The tap density and electrode compaction density of the obtained samples Samples Tap density (g cm -3 ) Electrode compaction density (g cm -3 ) SiNDs/C 0.24 0.44 VG@SiNDs/C 0.22 0.47 MPCF@VG@SiNDs/C 0.82 1.38 Table S3 The first CE (%), reversible capacity (mAh g -1 ), and capacity retention (%) after 100 cycles of the obtained samples    Table S5 Comparison of electrochemical performances of MPCF@VG@SiNDs/C with previously reported Si/C composites for LIBs anodes under industrial electrode conditions in open reports.CC-final charge capacity (mAh g -1 ), ICE-initial Coulombic efficiency (%), CR-capacity retention (%), ML-mass loading (mg cm -2 ), Ac-areal capacity (mAh cm -2 ), J-current density (A g -1 ), NC-cycle number, NA-not available    According to Fig. S28a, the rate capacities of MPCF@SiNDs/C at 0.1, 0.2, 0.5, 1, 2, 5, 10, and 20 A g -1 are 1430.6, 1321.4, 1252.7, 1183.6, 1054.1, 872.2, 756.1, and 572.7 mAh g -1 , respectively.By comparison with the rate performance of MPCF@VG@SiNDs/C in Fig. 3c, it can be concluded that the rate capacities of MPCF@VG@SiNDs/C are much higher than MPCF@SiNDs/C, demonstrating the important role of VG on Li-ion transport.Before cycling (Fig. S28b), the value of Rct of MPCF@SiNDs/C is larger than MPCF@VG@SiNDs/C, further confirming the significant advantages of MPCF@VG@SiNDs/C on charge transport capability.To compare the Li + storage kinetics in MPCF@SiNDs/C and MPCF@VG@SiNDs/C electrodes, we perform CV measurements on MPCF@SiNDs/C electrode with sweeping rates ranging from 0.1 to 20 mV s −1 (Fig.

Nano-Micro Letters
S16/S20 S29a).For MPCF@SiNDs/C, b values are calculated to be 0.81 and 0.73 for peaks 1 and 2, respectively (Fig. S29b), which are lower than those of MPCF@VG@SiNDs/C electrode (b values are calculated to be 0.91 and 0.84 for peaks 1 and 2, respectively, Fig. 4e).This result demonstrates that the MPCF@VG@SiNDs/C electrode has a higher capacitive contribution on capacity compared to MPCF@SiNDs/C electrode.As the scan rate increases from 0.1 to 20 mV s -1 , the contribution of capacitance rises from 44.1% to 82.6% for the MPCF@SiNDs/C electrode (Fig. S29c), which is much lower than MPCF@VG@SiNDs/C electrode (46.9 to 96.5%, Fig. 4f).The higher capacitive contribution is beneficial for obtaining higher capacity and better rate capability.These results indicate that MPCF@VG@SiNDs/C has a significant advantage over MPCF@SiNDs/C in promoting Li-ion transport.S7 The specific testing conditions in full cell.The full cells are charged to 4.2 V at a current density; afterward, a constant voltage is applied at 4.2 V with a cut-off relatively low current density.Then, after 5 min quiescence, the full cells are discharged to 2.8 V at a current density The gravimetric energy density can be obtained according to Eq. S1 [S1, S2].
The volumetric energy density of the full cell obeys Eq.S2 [S3].

Fig. S1
Fig. S1 Static sealed box furnace for the production of the SiNDs/C

Fig. S6
Fig. S6 SEM images of the SiNDs/C nanospheres

Fig. S9
Fig. S9 SEM images of the VG@SiNDs/C

Fig. S18 Nano
Fig. S18 Top-view SEM images of the SiNDs/C electrodes a before and b after 100 cycles at 0.1 A g -1 .Side-view SEM images of the SiNDs/C electrodes c before and d after 100 cycles at 0.1 A g -1

Fig. S22
Fig. S22 The electrochemical kinetic analysis of SiNDs/C: a CV curves at different sweep rates, b Log ip against Log v at marked peaks, c The percentages of pseudocapacitive contribution at different sweep rates

Fig. S24
Fig. S24 The finite element model established for uniform distribution of crystalline/amorphous Si nanodots in amorphous carbon nanospheres

Fig. S27
Fig. S27 SEM images a-c and corresponding EDS images d-f of MPCF@SiNDs/C

Fig. S29
Fig. S29 The electrochemical kinetic analysis of MPCF@SiNDs/C: a CV curves at different sweep rates, b Log ip against Log v at marked peaks, c The percentages of pseudocapacitive contribution at different sweep rates

Fig.
Fig. S30 a, b, c SEM images of the NCM811.d Galvanostatic charge/discharge voltage curves at 0.1 C, e cycling performance at 0.1 C, and f rate performance of the NCM811

Table S4
Rs, Rct, Rf, and the slop of the sloping line of electrodes in low-frequency region before cycling and after cycling.The data are from the fitted circuit of EIS spectra in the manuscript in Figs.3g-i MPCF@VG@SiNDs/C, after the 1st cycling 2.0 33.4 5.2 4.0 SiNDs/C, after testing rate cycling 5.5 33.6 15.6 1.0 VG@SiNDs/C, after testing rate cycling 3.5 20.1 8.1 1.6MPCF@VG@SiNDs/C, after testing rate cycling

Table S6 Comparison of electrochemical performances
of MPCF@VG@SiNDs/C with previously reported Si/C composites for LIBs anodes under non-industrial electrode conditions in open reports.CR1-capacity retention (%) in cycling performances, CR2-capacity retention (%) relative to capacity obtained at the lowest current density in rate performances, ML-mass loading (mg cm -2 ), Ac-areal capacity (mAh cm -2 ) calculated at low current density, J-current density (A g -1 ), NC-cycle number, NA-not available.

Table S8
Fast-charging performances of various materials in full cells.CR-Capacity retention (%) compared with the pristine value obtained at 0.1 C, Cycle number-CN, Jcurrent density (C)

Table S9
Comparison of cycling stability of various materials under high current densities in full cells.CR-Capacity retention (%), Cycle mumber-NC, J-current density (C)

Table S10
Comparison of EV and EG of our full cells with previosuly reported full cells when Si/C composites as anode materials in LIBs based